Which Old English dialect is Beowulf chiefly written in?

Beowulf is chiefly written in the West Saxon dialect of Old English.

More precisely, the surviving text predominantly uses Late West Saxon, the prestigious written variety that became influential in later Anglo-Saxon England. West Saxon was associated with the kingdom of Wessex and with important centers of learning such as Winchester, so scribes often copied literary works into that form even when the works originated elsewhere.

The answer should not be taken to mean that every word in Beowulf is purely West Saxon. The poem contains Mercian, Northumbrian, Kentish, Early West Saxon, and other linguistic features. This mixture has led scholars to propose a long and complicated transmission history, with the poem possibly composed or reshaped in another dialect before being copied into the surviving form.

The manuscript itself was written by two scribes. The first regularized much of the spelling toward common West Saxon, while the second retained more archaic and dialectal features. Thus “West Saxon” is the fair quiz answer, while “Late West Saxon” is the more precise description of the manuscript’s dominant written language.